35 research outputs found
A mathematical model for top-shelf vertigo: the role of sedimenting otoconia in BPPV
Benign Paroxysmal Positional Vertigo (BPPV) is a mechanical disorder of the
vestibular system in which calcite particles called otoconia interfere with the
mechanical functioning of the fluid-filled semicircular canals normally used to
sense rotation. Using hydrodynamic models, we examine the two mechanisms
proposed by the medical community for BPPV: cupulolithiasis, in which otoconia
attach directly to the cupula (a sensory membrane), and canalithiasis, in which
otoconia settle through the canals and exert a fluid pressure across the
cupula. We utilize known hydrodynamic calculations and make reasonable
geometric and physical approximations to derive an expression for the
transcupular pressure exerted by a settling solid particle in
canalithiasis. By tracking settling otoconia in a two-dimensional model
geometry, the cupular volume displacement and associated eye response
(nystagmus) can be calculated quantitatively. Several important features
emerge: 1) A pressure amplification occurs as otoconia enter a narrowing duct;
2) An average-sized otoconium requires approximately five seconds to settle
through the wide ampulla, where is not amplified, which suggests a
mechanism for the observed latency of BPPV; and 3) An average-sized otoconium
beginning below the center of the cupula can cause a volumetric cupular
displacement on the order of 30 pL, with nystagmus of order /s, which
is approximately the threshold for sensation. Larger cupular volume
displacement and nystagmus could result from larger and/or multiple otoconia.Comment: 15 pages, 5 Figures updated, to be published in J. Biomechanic
Trapping \u3ci\u3ePhyllophaga \u3c/i\u3espp. (Coleoptera: Scarabaeidae: Melolonthinae) in the United States and Canada using sex attractants.
The sex pheromone of the scarab beetle, Phyllophaga anxia, is a blend of the methyl esters of two amino acids, L-valine and L-isoleucine. A field trapping study was conducted, deploying different blends of the two compounds at 59 locations in the United States and Canada. More than 57,000 males of 61 Phyllophaga species (Coleoptera: Scarabaeidae: Melolonthinae) were captured and identified. Three major findings included: (1) widespread use of the two compounds [of the 147 Phyllophaga (sensu stricto) species found in the United States and Canada, males of nearly 40% were captured]; (2) in most species intraspecific male response to the pheromone blends was stable between years and over geography; and (3) an unusual pheromone polymorphism was described from P. anxia. Populations at some locations were captured with L-valine methyl ester alone, whereas populations at other locations were captured with L-isoleucine methyl ester alone. At additional locations, the L-valine methyl ester-responding populations and the L-isoleucine methyl ester-responding populations were both present, producing a bimodal capture curve. In southeastern Massachusetts and in Rhode Island, in the United States, P. anxia males were captured with blends of L-valine methyl ester and L-isoleucine methyl ester
HIV Disclosure Anxiety:A Systematic Review and Theoretical Synthesis
HIV disclosure can help people living with HIV to access social support, enhance antiretroviral adherence, facilitate engagement in care and reduce unprotected sex. Given interpersonal risks associated with HIV disclosure, however, anxiety about sharing one’s status is common. To investigate anxiety about HIV disclosure in HIV-positive populations, we conducted a systematic review of qualitative and quantitative studies, with 119 studies included. The review demonstrated that perceived interpersonal risks are associated with HIV disclosure and outlined evidence of associations with anxiety, fear and worry. We present a new cognitive model of HIV disclosure anxiety adapted from clinical theories of health and social anxiety, consistent with evidence from the review. The model attempts to explain the development and maintenance of anxiety in individuals whose functioning is most affected by concerns about sharing their status. Implications for helping people living with HIV struggling with significant levels of anxiety about HIV disclosure are discussed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10461-016-1453-3) contains supplementary material, which is available to authorized users
Tunable Light-Emitting Diodes Utilizing Quantum-Confined Layered Perovskite Emitters
Organic–inorganic
perovskites have been shown to have excellent optoelectronic properties.
Further, layered perovskites have been demonstrated, utilizing quantum
confinement to achieve emission blue-shifted from the bulk band gap.
Here, we tune this blue-shift to build LEDs that span the visible
spectrum. We demonstrate that electroluminescence from red-shifted
layers dominates emission from mixed-thickness devices and that the
addition of excess ligand is necessary to drive emission toward blue-shifted
layers. By tuning the thickness of the layers, we build LEDs with
blue emission utilizing the lead bromide system and orange emission
utilizing the lead iodide system. Finally, we demonstrate that these
materials suffer reversible degradation under an applied electric
field. The spectrally narrow emission, combined with the favorable
electronic properties of perovskite materials and access to shorter
emission wavelengths through quantum confinement, demonstrates the
promise of these materials as a new platform for low-cost, high-performance
light-emitting devices
Convergent and divergent evolution of genomic imprinting in the marsupial <it>Monodelphis domestica</it>
<p>Abstract</p> <p>Background</p> <p>Genomic imprinting is an epigenetic phenomenon resulting in parent-of-origin specific monoallelic gene expression. It is postulated to have evolved in placental mammals to modulate intrauterine resource allocation to the offspring. In this study, we determined the imprint status of metatherian orthologues of eutherian imprinted genes.</p> <p>Results</p> <p><it>L3MBTL</it> and <it>HTR2A</it> were shown to be imprinted in <it>Monodelphis domestica</it> (the gray short-tailed opossum). <it>MEST</it> expressed a monoallelic and a biallelic transcript, as in eutherians. In contrast, <it>IMPACT, COPG2,</it> and <it>PLAGL1</it> were not imprinted in the opossum. Differentially methylated regions (DMRs) involved in regulating imprinting in eutherians were not found at any of the new imprinted loci in the opossum. Interestingly, a novel DMR was identified in intron 11 of the imprinted <it>IGF2R</it> gene, but this was not conserved in eutherians. The promoter regions of the imprinted genes in the opossum were enriched for the activating histone modification H3 Lysine 4 dimethylation.</p> <p>Conclusions</p> <p>The phenomenon of genomic imprinting is conserved in Therians, but the marked difference in the number and location of imprinted genes and DMRs between metatherians and eutherians indicates that imprinting is not fully conserved between the two Therian infra-classes. The identification of a novel DMR at a non-conserved location as well as the first demonstration of histone modifications at imprinted loci in the opossum suggest that genomic imprinting may have evolved in a common ancestor of these two Therian infra-classes with subsequent divergence of regulatory mechanisms in the two lineages.</p
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A Nanobionic Light-Emitting Plant.
The engineering of living plants for visible light emission and sustainable illumination is compelling because plants possess independent energy generation and storage mechanisms and autonomous self-repair. Herein, we demonstrate a plant nanobionic approach that enables exceptional luminosity and lifetime utilizing four chemically interacting nanoparticles, including firefly luciferase conjugated silica (SNP-Luc), d-luciferin releasing poly(lactic-co-glycolic acid) (PLGA-LH2), coenzyme A functionalized chitosan (CS-CoA) and semiconductor nanocrystal phosphors for longer wavelength modulation. An in vitro kinetic model incorporating the release rates of the nanoparticles is developed to maximize the chemiluminescent lifetimes to exceed 21.5 h. In watercress (Nasturtium officinale) and other species, the nanoparticles circumvent limitations such as luciferin toxicity above 400 μM and colocalization of enzymatic reactions near high adenosine triphosphate (ATP) production. Pressurized bath infusion of nanoparticles (PBIN) is introduced to deliver a mixture of nanoparticles to the entire living plant, well described using a nanofluidic mathematical model. We rationally design nanoparticle size and charge to control localization within distinct tissues compartments with 10 nm nanoparticles localizing within the leaf mesophyll and stomata guard cells, and those larger than 100 nm segregated in the leaf mesophyll. The results are mature watercress plants that emit greater than 1.44 × 1012 photons/sec or 50% of 1 μW commercial luminescent diodes and modulate "off" and "on" states by chemical addition of dehydroluciferin and coenzyme A, respectively. We show that CdSe nanocrystals can shift the chemiluminescent emission to 760 nm enabling near-infrared (nIR) signaling. These results advance the viability of nanobionic plants as self-powered photonics, direct and indirect light sources